The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
An exterior trim for a motor vehicle may include a rigid substrate or support member that has an outer decorative surface and an inner support surface. The outer decorative surface may have a high quality finish, such as a glossy surface. A translucent or transparent coating may be applied overtop the outer decorative surface of the substrate. The inner support surface includes flanges and other features to fasten the exterior trim to the motor vehicle and to provide structural rigidity to the substrate. Exterior trim for motor vehicles may include human machine interface (HMI) devices used to externally control certain features of the motor vehicle. To support these HMI devices, the substrate may include additional features, such as a structural wall that supports a display for displaying information to a user or a physical input unit for receiving physical input from a user.
The exterior trim is commonly constructed by injection molding techniques in which the material for the substrate is injected into a preformed mold. Rigidity and strength for the structural walls of a substrate is achieved by molding the structural wall thicker than the thickness of the substrate itself. However, if the structural wall is thicker than the substrate thickness, as the molded material cools, the structural wall may cool at a rate that is different than that of the rest of the substrate. When these cooling rates differ, the structural wall may shrink at a rate that is different than that of the rest of the substrate. The structural wall may then pull on the substrate, causing surface divots to appear on the exterior surface of the substrate. To avoid the creation of surface divots, the structural wall may also be molded thinner than the substrate thickness. However, if the structural wall is molded thinner than the substrate thickness, the rigidity and strength of the substrate may be compromised.
While conventional exterior trims are effective, there is room for improved exterior trims that ensure an appropriate amount of structural rigidity without causing surface divots on the exterior surfaces of exterior trims.